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Registered 2006 SLK280
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55 Posts
Discussion Starter #1
I’ve seen a few posts where folks say they are getting 30+ MPG with their SLK. I’ve got an 06 SLK280 with 95k miles and have averaged 20.9 MPG over the last 5k miles. I’ve been driving in S mode but I don’t feel like I have a lead foot. Am I missing something? It’s got fresh oil and the stock Mann air filter. Just changed the transmission fluid but I haven’t noticed a difference in gas.
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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99,675 Posts

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Premium Member 2004 SLK350
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4,961 Posts
Ignition ( spark plugs and coils ), lambda's, maf ( a new one ) and last will be injectors ( need to be checked).
See what STFT and LTFT you have
 

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Super Moderator CA 2012 SLK55 AMG w/P30
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14,773 Posts
A lot of city driving (stopngo) affects it a lot.
My '55 was tested at 60 mph on cruise, no air, windows and roof up gets a smidge over 38MPG (imperial not US). You should do better (y) (converted to US, mine is 31.7 mpg as the US gallon is smaller than our imperial measurement). Keep in mind: this was just a TEST. No way do I drive like that normally 😉

That is with 4 cyl de-activation enabled. Dunno if it was standard or not--you have it?

R172 MPG.jpg
 

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Registered 2009 SLK280
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362 Posts
I have a 2009 280 and average around the 30 mpg mark. No motorway driving or heavy traffic and a mix of cruising and spirited driving.
 

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Super Moderator 2013 SLK350
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1,715 Posts
Just completed a ~1200 mile road trip, mostly freeway but lots of in-city stop n go. Looks like I averaged 24.5 mpg, which for me is super good, seeing that I am in "S" and "M" most of the drive. MPG and driving pleasure/excitement may be incongruent... :p ;)
 

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Premium Member 2007 SLK350
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914 Posts
I have the 350 (2007) which I think has basically the same engine and the intake tumbler flaps were broken (no errors on the dash but a good code reader will show this), before being fixed I was getting low 20mpg and now get 33+mpg. So worth getting this checked.
Also US and UK mpg are different depending on how your gallons are measured.

US 20.9mpg = UK 25mpg
 

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Super Moderator UK SLK 55 AMG 2007
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29,580 Posts
350 2009.
Low on tippy tappy in S mode, hitting the lanes as they were meant to be used, circa 14-15 mpg.
You can get it lower if you really push.
Mixing it with town, lanes, queues 28-35.
Auto in S mode on long motorway run 80-90 ish gives 35-42.

If you accelerate AND brake hard you bring it down quickly.
Accelerate hard but avoid hard braking guestimate high 20s, low 30s.
 

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Super Moderator UK SLK 55 AMG 2007
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29,580 Posts
You need to be more like Sarge, he manages to get single digits!
He spent a lot of money, to spend a lot more money on fuel.

nb You can get single digits on both the 350 and 55 in manual mode.
You also get to chat with our friendly judge too.
 

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Registered 2006 SLK280
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55 Posts
Discussion Starter #12
I have the 350 (2007) which I think has basically the same engine and the intake tumbler flaps were broken (no errors on the dash but a good code reader will show this), before being fixed I was getting low 20mpg and now get 33+mpg. So worth getting this checked.
Also US and UK mpg are different depending on how your gallons are measured.

US 20.9mpg = UK 25mpg
So I just pulled the codes and I have a P2006. I will check the bell crank tomorrow when the sun comes up. I am leaning towards a complete manifold replacement since the car has 100k miles. Are there any performance intakes out there or should I just get the Rock Auto OEM?
 

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Premium Member 2007 SLK350
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914 Posts
So I just pulled the codes and I have a P2006. I will check the bell crank tomorrow when the sun comes up. I am leaning towards a complete manifold replacement since the car has 100k miles. Are there any performance intakes out there or should I just get the Rock Auto OEM?
That will be it then. Once I had fixed mine I also noticed much more power so well worth fixing.
I really wouldn’t bother with a new manifold, the only part that normally gives problems is the plastic crank. Purchase a good quality metal replacement (I used one with the standard ‘cups’ for the 2 control arms rather than the cheaper units that have bolts or pins as these can rub) and the 2 gaskets, then read the many great posts on here about doing the job, it’s not bad if you’re confident about pulling cars apart, just take your time.
edit- this unit seems good as it’s still low profile where the bars join the crank FOR Mercedes M272 V6 M273 V8 Intake Manifold Air Flap Runner Lever Repair Kit | eBay
 
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Registered 2006 SLK280
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55 Posts
Discussion Starter #14
That will be it then. Once I had fixed mine I also noticed much more power so well worth fixing.
I really wouldn’t bother with a new manifold, the only part that normally gives problems is the plastic crank. Purchase a good quality metal replacement (I used one with the standard ‘cups’ for the 2 control arms rather than the cheaper units that have bolts or pins as these can rub) and the 2 gaskets, then read the many great posts on here about doing the job, it’s not bad if you’re confident about pulling cars apart, just take your time.
edit- this unit seems good as it’s still low profile where the bars join the crank FOR Mercedes M272 V6 M273 V8 Intake Manifold Air Flap Runner Lever Repair Kit | eBay
After reading more it sounds like the flaps never go bad, it’s always the plastic triangle. I went ahead and ordered the $150 Uro kit from Amazon since it makes sense to me to replace the actuator with a metal piece as well while I’m in there. Stopped by the dealership today and got the three gaskets for $25. I’ll probably knock out the spark plugs while I’m messing around too. I’ll probably knock this out on Saturday- will post if I notice a mileage or power boost after.
 

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Premium Member 2004 SLK350
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4,961 Posts
You have all the info on how to do it here. Did this job a few times on different cars
 

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Registered 2006 SLK280
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55 Posts
Discussion Starter #16 (Edited)
Got the Uro kit swapped and the intake reinstalled. Used zip ties on the three front holes to hold the gaskets in place. Started up OK and ran well today but now I have a pending P2015 code which is also the tumble flap bank 1a fail. I checked all the vacuum connections as well as the sensor plug under the wire harness on the rear of the intake. Reset the codes, will see if it comes back. Any ideas on the code? I saw a couple of threads but it looks like their solution was just a new intake. I checked both flaps while the intake was off and they are easy to turn, no binding.
Gas mileage on my drive this morning was about 10% better than I normally get.
Long term fuel trim 1 is 6.3, LTFT 2 is 2.3 I’ll keep an eye to see if those drop
 
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